Semiconductor devices such as logic and memory devices are typically fabricated by a sequence of processing steps applied to a specimen. The various features and multiple structural levels of the semiconductor devices are formed by these processing steps. For example, lithography among others is one semiconductor fabrication process that involves generating a pattern on a semiconductor wafer. Additional examples of semiconductor fabrication processes include, but are not limited to, chemical-mechanical polishing, etch, deposition, and ion implantation. Multiple semiconductor devices may be fabricated on a single semiconductor wafer and then separated into individual semiconductor devices.
Metrology processes are used at various steps during a semiconductor manufacturing process to detect defects on wafers to promote higher yield. Optical metrology techniques offer the potential for high throughput measurement without the risk of sample destruction. A number of optical metrology based techniques including scatterometry and reflectometry implementations and associated analysis algorithms are commonly used to characterize critical dimensions, film thicknesses, composition and other parameters of nanoscale structures.
In one example, two-dimensional beam profile reflectometers (2D-BPR) systems are employed to perform measurements of semiconductor samples. However, existing 2D-BPR systems acquire measurement signals one wavelength at a time. This limits the throughput of such systems when multiple illumination wavelengths are needed to accurately characterize the sample.
In another example, spectroscopic ellipsometry (SE) systems perform simultaneous measurements across a broad spectrum of illumination wavelengths. However, existing SE systems acquire measurement signals at one angle of incidence (AOI) at a time. This limits the throughput of such system when multiple AOIs are required to accurately characterize the sample.
Metrology applications involving the measurement of structures generated by semiconductor fabrication processes present challenges due to increasingly small resolution requirements, multi-parameter correlation, increasingly complex geometric structures, and increasing use of opaque materials. Thus, methods and systems for improved measurements are desired.